1. Field of the Invention
The present invention is generally related to a speed control method for a vehicle and, more particularly, to a method for maintaining an average speed of a marine vessel during a preselected period of time such as the course followed by a marine vessel during a water sport competition.
2. Description of the Prior Art
Many different types of speed control methods are known to those skilled in the art. U.S. Pat. No. 6,109,986, which issued to Gaynor et al on Aug. 29, 2000, discloses an idle speed control system for a marine propulsion system. The idle speed control system controls the amount of fuel injected into the combustion chamber of an engine cylinder as a function of the error between a selected target speed and an actual speed. The speed can either be an engine speed, measured in revolutions per minute, or it can be boat speed, measured in nautical miles per mile or kilometers per hour. By comparing target speed to actual speed, the control system selects an appropriate pulse width for the injection of fuel into the combustion chamber and regulates the speed by increasing or decreasing the pulse width.
U.S. Pat. No. 5,765,528, which issued to Kamimaru on Jun. 16, 1998, describes an idle speed control system for automotive internal combustion engines. During idling of an internal combustion engine, when there is a difference between an actual engine speed and a target idle speed which is preset in accordance with an engine load, the opening and closing timings of an intake/exhaust valve of the engine is changed in accordance with the difference between the actual engine speed and the target idle speed to change an intake air flow sucked into the engine. Therefore, it is not required to provide any apparatus, such ISC valve, provided in conventional systems, and it is possible to quickly adjust the engine speed so as to be equal to the target idle speed.
U.S. Pat. No. 5,362,263, which issued to Petty on Nov. 8, 1994, describes a trolling autopilot. The autopilot is for a vessel and for use in combination with a depth finder having a transducer, including a means for setting and storing a desired characteristic to be followed by the vessel, means for measuring the characteristic to be followed by the vessel, and means for storing a signal generated by the measuring means indicative of the measured characteristic. Once received and stored, the measured characteristic is compared to the selected characteristic. Based upon the comparison between the two characteristics, at least one servo motor is actuated to alter the direction the vessel is traveling. A servo motor may be coupled to the helm or to an outboard motor mounted to the vessel. The speed of the vessel may also be controlled based upon a comparison between a measured value and a selected value.
U.S. Pat. No. 5,364,322, which issued to Fukui on Nov. 15, 1994, describes a control apparatus for a marine engine. The apparatus is capable of effectively suppressing a great variation in the rotational speed of the engine due to a great variation in an intake air pressure particularly when the engine is trolling. In one form, an air/fuel ratio of a mixture supplied to the engine is made constant to maintain engine output power at a constant level. In another form, the intake air pressure, based on which the engine is controlled, is averaged in such a manner as to reduce a variation in the engine rotational speed by using a greater averaging coefficient during trolling than at other times. In a further form, if a variation in the intake air pressure is less than a predetermined value, the intake air pressure is used controlling the engine, whereas if otherwise, another engine operating parameter such as an opening degree of a throttle valve is used instead of the intake air pressure.
U.S. Pat. No. 5,546,188, which issued to Wangler et al on Aug. 13, 1996, describes an intelligent vehicle highway system sensor and method. An object sensor and method using pulsed laser range imaging technology is adapted for determining the velocity and three dimensional profile of a vehicle passing the sensor for classifying the type of vehicle for use in Intelligent Vehicle Highway Systems. A pair of scanned laser beams are provided by splitting a continuously pulsed laser beam from a transmitter and an optical receiver determines the presence of a vehicle in a predetermined zone such as a highway weigh station or toll booth. Range, angle and time data are collected and stored for use in determining the speed of the vehicle passing the sensor and its three dimensional profile. Forward and backward scanned beams are provided using alternate embodiments of a rotation mirror and using two transmitters/receivers in another embodiment. The pulsed energy is sent into two divergent beams, which are received as reflective energy in a receiver. The receiver accepts reflections from the beams and provides inputs for purposes of determining time of flight, and for measuring the time interval between interceptions of the two divergent beams for a given vehicle. An encoder tracks the position of the mirror for providing angle data with associated range measurements. The vehicle speed is calculated for range data collected when the vehicle passes through the forward and backward scanned beams. Three dimensional profiles are compared with preselected vehicle profiles for classifying the vehicle.
U.S. Pat. No. 5,957,992, which issued to Kiyono on Sep. 28, 1999, describes a vehicle cruise control system and method having improved target speed resolution feature. A vehicular constant-speed running system converges a vehicle speed control of a vehicle quickly to a target vehicle speed when the vehicle is set in a cruise control mode. The vehicular constant-speed running system includes a constant-speed running section for controlling a throttle opening independently of an accelerator opening to maintain a vehicle at a target vehicle speed. It is also an initial opening setting section which, at the time of transfer by the constant-speed running section, sets the throttle opening before the transfer of an initial value at the time of the transfer if the throttle opening is in a region which is preset based on either the vehicle speed at the time of the transfer or a parameter correlated with the vehicle speed. If the throttle opening is not in this region, the initial opening setting section sets the same throttle opening to the upper limit and/or the lower limit of that region.
U.S. Pat. No. 5,680,309, which issued to Rauznitz et al on Oct. 21, 1997, describes a control system for automatic resumption of speed control after gear change. The method for automatically resuming vehicle speed control after a gear change of the vehicle""s manual transmission is disclosed. The method may be implemented as a subroutine in the vehicle""s general control software. After disengagement of the clutch, the subroutine suspends the automatic speed control system and then periodically checks to determine if the driver has shifted gears within a predetermined time period. This determination is made by checking to see if the clutch has once again been engaged with the transmission in gear. If this occurs within the predetermined time period, then the control system automatically resumes the speed control of the engine. The determination of whether the transmission has been placed into another gear is made by an explanation of calculated gear ratios, rather than by the addition of a hardware sensor.
U.S. Pat. No. 5,624,005, which issued to Torii on Apr. 29, 1997, describes a running speed control device for a vehicle. When an xe2x80x9coffxe2x80x9d state of an idle switch is detected even once after an ignition switch of an internal combustion engine is turned on, a cruise ECU determines that the idle switch is normal, and performs constant-speed cruise control if the start thereof is instructed. Because the constant-speed cruise control is normally instructed while a vehicle is running, if the idle switch is normal, the idle switch becomes the xe2x80x9coffxe2x80x9d state at least one time during the time period until the start of the constant-speed cruise control is instructed after the ignition switch is turned on. For this reason, if the idle switch does not become the xe2x80x9coffxe2x80x9d state even once, the cruise ECU determines that the idle switch has failed and interrupts the constant-speed cruise control.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
Known cruise control systems typically provide a method of regulating the speed of a vehicle to a target speed without concern with the average speed of the vehicle over a preselected time or distance. For example, if a target speed of 50 miles per hour (MPH) is set for a vehicle, known cruise control algorithms react to a deviation from the target speed by regulating the vehicle speed back to the target speed. In other words, if the cruise control algorithm detects that the vehicle actually is traveling at 49 miles per hour, when the target speed is 50 miles per hour, the algorithm will take steps to increase the speed of the vehicle to 50 miles per hour. Regardless of the specific methodology employed to accomplish this task, known cruise control systems attempt to reestablish the target speed when a deviation in speed is sensed.
In certain situations, such as timed water sport competition, a requirement is set that the vehicle maintain a certain average speed over a predefined course. In these circumstances, a deviation from the targeted average speed, followed by a known type of cruise control method attempt to reestablish the target speed, will be ineffective in achieving the overall average target speed required for the competition.
It would therefore be significantly beneficial if a speed control method could be provided which assures the achievement of an average speed over a predefined distance or over a preselected time period, in which a vehicle traveling over a predefined competition course will satisfy the required time period at precisely the time when the vehicle completely traverses the length of the competition course.
A method for controlling the average speed of a vehicle performed in accordance with the present invention, comprises the steps of measuring elapsed time, defining a desired average speed, measuring an actual speed of the vehicle, and calculating an error magnitude as a function of the desired actual speed and the actual speed. The method of the present invention further comprises the steps of determining a cumulative error magnitude of the vehicle as a function of both the error magnitude and the elapsed time and then selecting a period of elapsed time over which an absolute value of the cumulative error magnitude is to be reduced to a predetermined magnitude, such as zero. The method of the present invention further comprises the step of determining a compensatory speed of the vehicle, as a function of the cumulative error and the period of elapsed time, which will reduce the cumulative error magnitude to the predetermined magnitude with in the selected period of elapsed time.
In a preferred embodiment of the present invention, the vehicle is a marine vessel and the timed measuring step, the error magnitude calculating step, the cumulative error determining step, and the compensatory speed determining step are all performed by a microprocessor. The microprocessor can be part of an engine control unit (ECU) of an engine.
A particularly preferred embodiment of the present invention further comprises the steps of sensing a starting signal and iterating the steps of the present invention repeatedly for a preselected period of time subsequent to the starting signal sensing step. The actual speed can be measured by a sonar device, a radar device, or a global positioning satellite (GPS) system. In a particularly effective embodiment of the present invention, the desired average speed, the actual speed, and the compensatory speed are all land-based speeds.
In certain embodiments of the present invention, the actual speed measuring step can comprise the steps of measuring a first distance from the vehicle to an object fixed to the land, measuring a first speed of the vehicle relative to the object, and calculating the actual speed of the vehicle as a function of the first distance and the first speed. The first period of elapsed time over which the absolute value of the cumulative error magnitude is to be reduced to a predetermined magnitude, such as zero, is selected as a function of a predetermined length of a course over which the vehicle must maintain the average speed during a competition.